Hydraulic apparatus



June 22, 1965 T. BUDZICH HYDRAULIC APPARATUS 2 Sheets-Sheet 2 Filed Feb. 11, 1963 w... E, x r I I4 1/ l7 INVENTOR MFp x 'Fp 05032 BUDZ/CH MFp=0 3,190,232- Patented June 22, 1965 3,190,232 HYDRAULIC APPARATUS Tadeusz Budzich, 3344 Colwyn Road, Cleveland, Ohio Filed Feb. 11, 1963, Ser. No. 257,699 12 Claims. (Cl. 103-162) This invention relates to controls for variable displacement pumps and more particularly to a constant pressure control for a variable displacement pump.

In still more particular aspects this invention relates to a constant pressure control for a variable displacement pump in which the volume changing mechanism is actuated through the forces developed in the pumping mechanism.

Axial piston pumps employing tiltable cam plates to vary the pump displacement are well known in the art. The tilting of the cam plate is usually achieved by a fluid pressure piston cylinder arrangement for tilting the cam plate against the bias of a spring. A pressure signal from a control is introduced into fluid cylinder to vary the pump displacement. This type of arrangement suffers fromthe following disadvantages. The size of the control pistons used in tilting the cam plate is limited by the size of an acceptable envelope. This limits the level of the operating force transmitted to the cam plate resulting in a comparatively slow responding control.

With large control pistons, although the actuating force level is substantially increased, time is lost in supplying large volume of oil to actuate such a control which also results in a slow responding control.

In the present invention the tilting of the cam plate is obtained without the use of a conventional control piston cylinder arrangement directly operating the cam plate, but rather by changing the centroid of the pumping reaction forces normally developed on the tiltable cam plate in respect to the axis of rotation of the tiltable cam plate. The centroid of the reaction pump-' ing forces is moved by rotating (through a small angle) a control plate interposed between the valve plate and cylinder barrel of the pump. In this way large tilting forces can be developed on the cam plate while utilizing the basic components of the pumping mechanism.

Pumps employing the principle of valve plate rotation to divert the oil from the pumping cylinders tothe suction cylinders are well known in the art. In those devices when rotating the valve plate through 90 while maintaining the stroke of the pistons constant, a change from zero to maximum eifective pump displacement is possible.

In the present invention a control plate between the barrel and valve plate is rotated through a very small angle not to bypass the fluid from the pump discharge to the suction zone, but rather to tilt the cam plate by unbalancing the pumping reaction forces acting on the cam plate in respect to the axis of its suspension.

It is therefore an object of the present invention to provide a constant pressure control of a variable displacement pump in which the signal to change pump displacement to maintain a constant output pressure changes the force distribution in the pumping mechanism to actuate the displacement changing mechanism.

Another object of this invention is to provide a displacement changing mechanism of a variable displacement pump which is actuated by the pumping forces developed inside the pumping cylinders.

Still another object of this invention is to provide actuation of the displacement changing mechanism of a pump by moving the centroid of the pumping forces developed inside the pumping cylinders in respect to the axis of suspension of the cam plate, whereby large turning moments can be developed in the displacement changing mechanism. a

These and other objects as well as complete understanding of the invention will be apparent from'a consideration of the following description and drawings in which:

FIGURE 1 is a longitudinal sectional view through an axial piston variable displacement pump embodying this invention.

FIGURE 2 is a sectional view taken substantially along the line 22 of FIGURE 1 showing the features of the control. 7

FIGURES 3a, 3b and 3c are diagrammatic representations of the forces developed on the cam plate by the position of the control plate when the pump is delivering full flow; and

FIGURES 4a, 4b and 4c are diagrammatic representations of the forces developed on the cam plate by the position of the control plate rotated through a small angle to reduce the flow of the pump.

Referring now to the drawings and particularly to FIGURES l and 2, a pump generally designated as 10 is shown having a housing 11 and a cover 12, which together define a chamber 13. A shaft 14 extends into the chamber 13 and is journalled by bearings 15 and 16, located in the cover 12 and housing 11 respectively. A runnion 17 is journalled on a pin 18 carried by the housing 11 and is provided with an opening 19 through which the shaft 14 extends. Angular tilting movement of trunnion 117 is limited by stops 20 and 21 provided on the cover =1-2. V The shaft '14 is equipped with splines 22 drivingly engaging a splined extension 23 of -a cylinder barrel 24. The cylinder barrel 24 has a multiplicity of cylinder bores 25in which pistons 26 are disposed. Pistons 26 have part spherical ends 27 universally mounting piston shoes 28 which operationally engage flat face 29 of the trunnion 17, the trunnion thus operating as a cam plate. Piston shoes 28 are maintained against the trunnion by a nutating plate 3% and retainer -31. The trunnion -17 has an extension '32 against which a biasing spring 33 works through a guide 34. The cylinder barrel 24 works in abutment with a control plate 35 having kidney shaped timing slots 36 and '37 (FIGURE 2). Cylinder bores 25 each tenminate in kidney shaped slots 38 which communicate with timing slots 36 and 37. The control plate 35 is journalled for limited rotation in respect to the housing 11 by a tubular support :39 and works in abutment with a sealing face 40 formed on the end'of the housing 11. Sealing face 46 is provided with a pair of kidney shaped passages 49a and 4% similar to timing slots 36 and 37. Passageyiila is connected to high pressure port 400 and passage 40b is connected to low pressure port 40d. The

7 control plate 35 has an actuating arm 41 equipped with a part spherical end 42 engaging a control piston 43 and a biasing piston 44. The biasing piston 44 is biased by a control spring 45 through control spring guide 46 and a ball 47. The'control spring '45 is located by control stop 48 which is slidably mounted in control spring bore 49 and sealed by an O ring 59. An adjusting screw 51 engaging the control stop 48 is retained in a cover 52 mounted by bolts 53 to the pump housing 1 1. The control spring bore 49 is vented by a passage not shown to chamber 13. The

control piston 43 is slidably guided in control bore 54.

Operation The trunnion 17- under the action of biasing spring 33 riving at a position as shown in FIGURE 1.

motion from the shaft 14 is transmitted through splines will tend to rotate around, pin 18 and engage stop 20 are The rotary 22 to cylinder barrel 24. v The rotation of cylinder barrel 24, in a well known mannen'will induce the reciprocating motion in the pistons 26 which with piston shoes 28 Will follow the flat surface 29 of trunnion 17. The reciprocating motion of the pistons-26 will displace fluid in cylinder slots 36 and 37 through slots 40a and 4tlb; a pumping action will be originated by the rotating shaft 14. The volume of the fluid taken from and displacedinto the timing slots 36 and 37 per one revolution of the shaft 14 will be proportionalto, the length of the stroke of the pistons 26 and therefore proportional to the angle of in-' clination of the trunnion17 inrespect to the axis of rotation of the shaft 14. The angular inclination of the trunnion 17 as shown in FIGURE 1 corresponds to the maximum displacement of the pump. When the trunnion 17 is 1.

- spect to thepump axis against a register of biasing spring rotated in a clockwise direction around pin18 to a position where the fiat face 29 is normal to the axis of rota;

tion the pump output will become zero.

The angular position of the trunnion 17 is dependent upon the balance between the moment of the reaction forces of the pistons on the trunnion and the moment caused by the force exerted by the spring 33. The cone in the net moment of the reaction forces of the pistons is induced by rotation of the control'plate 35. i Rotation of moves the position 64 of the resultant forceFp away] from trunnion axis of rotation 65. FIGURE 40 shows diagrammatically the force distribution acting on the trunnion .17 with control plate 35 :angularly disposed as shown in FIGURE 4a. Since the position t6'4 of resultant force 'Fp" is' now displaced by a distance x from the axis of rotation 65 of the trunnion 17, it will induce a. counter clockwise turning moment MFp as-shown whichwill decrease the trunnion angle with respect to the pump axiswhen it exceeds moment -Ms thus decreasing the pump output.

will change the magnitute of the moment Ms bycompressing the spring This will establish a balance be tween the moment Ms and moment Mp for any given position and magnitude of resultant force Fp. The. amount of rotation (tilt) caused by any given turning moment MFp'will be dependent upon the force of biasing spring '33 and the trunnion '17 will be rotated in a clockwise direction away from the stop 20, thus reducing the pump output. Thusa small rotation of the control plate 35 will change the position of the resultant forceFp acting on the .trunnioni? i'nrelation to the axis of rotation- 65 of trunnion '17 regulating'itsangular inclination in re- 33. The change in angular'inclination of trunnion 17 will proportionally change the displacement of the pump. To 1 increase the volume when the pump is delivering a re-' duced volume, the control plate is rotated the other way which will move the position of the resultant force -Fp back toward the axis 65. And; if fast response is de-' sired the control plate can be configured and arranged to move the force Fp past the axis 65.

The angle of the control plate 35 is regulated bya control signal which is developed by and proportional the controlplate will change the positionof the'timing, 7

slots 36 and 37 with respect to the axis of rotation (tilt) of the trunnion which will in turn change the position of the net resulting moment resulting in a tilting or turning movement. This change in net moment is shown diagrammatically in FIGURES 3a, 3b 3c, 4a, 4b, and 4c.

In FIGURE 3b the forces acting 'on the trunnion '17 are shown, the axis of rotation (tilt) of the trunnion being used as a reference line designated by the reference character 65. The. extension of the trunnion 17 is subjected to a force from the biasing spring 33, this force being designated as F: working at point 63. Thepoints W1, W2, W3, and W4 denote the reaction forces transmitted to trunnion 17 by pressure developed on the pistons 26 which are on the pumping stroke. The force Fp located at point 64 denotes the resultant force obtained from summation of forces W1,-W2,'W3 and W4 and constitutes the total hydraulic reaction force transmitted, to the trunnion 17 by the pumping pistons 26. FIGURE 3a shows 'theca'ngularirelationship of the control plate 35 and timing slots 36 and 37 to provide the forces on the trunnion 17in the position shown in FIGURE 3b. FIGURE shows diagrammatically the force, distribution acting on the trunnion 17 with control plate angularly'disposed as shown in FIGURE 3:: and the trunnion angularly disposed as shown in FIGURE 1. Since in this position of the control plate 35 the point 64 of resultant force Pp coincides with the I axis of rotation 65 of the trunnion pin '18 of trunnion 1'7 itwill be directly carried in the form of a bearing pressure on the pin 18 without inducing any turning moment to the trunnion .17; The force Fs, transmitted to the trun to the output pressure of the pump. This pressure signal 7 is developed 1n the pumping mechanism and is-transmitted to the control mechanism shown in FIGURE}; The control plate 35 is connected to actuating arm 41,

equipped with spherical end 42. Fluid under pressure from the timing slot 36 which is the high pressure slot is conducted through the drilling 60 to annular space 59 and through passage 58a to cylinder 57 slidably engaging force-piston 58. Since the end'of force piston 58in eon-1 tactwith the control piston 43- is subjected to a pressure. in control cylinder 54- which is vented by passage 55 to. chamber 13, the force piston 53 working as a fluid motor will transmit an axial force to control piston 43 proportional tothe pressure difference between timing slot36 andchamber 13. This force acting through the spherical end 42 of actuating arm 41 will'tend to induce a turningrnornent in control plate 35 journaled on tubular support: 39. The biasingpiston 44 will transmit to spherical end 42 of actuating arm 41 an opposing biasing force of control 'sprmg 45. With the force developed, due-to pressure existing in timing slot 36 on cross-section area of. force piston 58 smaller than the preload in the control spring I 45,.the control piston 43 will rest against the plug'55a and the control plate'35 will be maintained in a positionas shown in FIGURES Z'and 3a., This is a position equivalent to maximum pump displacement as shown'in FIG- URE 1.. Once the force developed on the force piston 58v is suflicient to overcome the preload in the control. spring 45, the control plate 35 will be rotated in a clockwise direction, theangle of rotation being proportional to the rise in pressure in timing slot'3 6; As explainedwhen re-i ferring to FIGURES 3a, 3b,;3c, 4a, 4b and 4c rotation of the control plate 35'will change the equilibrium of forces acting on the trunnion 17 turning it towards a position of reduced pump displacement. In this way, the 7 pump w1ll supply the maximum flow until the pressure developed in timing slot 36' reaches a predetermined value I equivalent to the preload in the control spring 45, which is adjustable by adjusting screw 51. Once this pressure is reached the pump will automaticallyreduce its flow with rise in discharge pressure, the flow of the pump becoming Rotation of the trunnion about the' pin '18 zero with the trunnion :17 reaching a perpendicular position in respect to axis of rotation of the shaft 14. Since the resultant force Fp in a pump constitutes the total hydraulic pumping reaction and therefore is very large, the

producing a fast responding control.

While one embodimentof this invention has been shown,

and described, various modifications and adaptations can be made without departing from the spirit and scope of the appended claims.

' What is claimed is: V V

1. A fluid pressure energy translating device comprising a housing having inlet. and outlet ports, a cylinder barrel rotatably mounted in said housing, pistons reciprocally disposed in said cylinder barrel, a cam plate mounted for tiltable movement in respect to the housing about an axis, biasing means normally urging said cam plate to tilt in one direction, valving means to sequentially connect said pistons with the inlet and outlet ports, said valving means including stationary support means, and fluid distributing means interposed between said stationary support means and said cylinder barrel, mounting means for said fluid distributing means to permit movement of said fluid"dist'ributing means in respect to said tiltable cam plate tochange the force moment of the pistons on the cam plate in respect to the axis of tilt of the cam plate, and actuation means to impart movement to said fluid distributing means to change the cant angle of thetiltable cam plate in response to change inthe' force moment of the pistons coactable with the cam plate.

2. A fluidpressure energy translating device compris ing a housing having inlet and outlet ports, a cylinder barrel rotatably mounted in said housing, pistons reciprocally disposed in said cylinder barrel, a cam plate mounted for tiltable movement in respect to the housing about an axis, biasing means normally urging said cam plate to tilt in one direction; valving means to sequentially connect said pistons with the inlet and outlet ports, said valving means including stationary support means, and fluid distributing means interposed between said stationary support means and said cylinder barrel, means journalling said fluid distributing means for rotation in respect to said cam plate to change the force moment of the pistons on the cam plate in respect to the axis of tilt of the cam plate, and actuation means'to rotate said fluid distributing means to change the cam angle of the tiltable cam plate in response to change in the force moment of the pistons coactable with the cam plate.

3. A fluid pressure energy translating device comprising a housing having inlet and outlet ports, a cylinder barrel rotatably mounted in said housing, pistons reciprocally disposed in said cylinder barrel, a cam plate mounted for tiltable movement in respect to the housing about an axis, biasing means normally urging said cam plate to tilt in one direction, valving means to sequentially connect said pistons with the inlet and outlet ports, said valving means including stationary support means, and fluid distributing means interposed between said stationary support means and said cylinder barrel, said distributing means including fluid conducting passages defining high and low pressure zones communicating with said inlet and outlet ports, means journalling said fluid distributing means for rotation in respect to said cam plate to change the force moment of the pistons on the cam plate in respect to the axis of tilt of the cam plate, and actuation means to rotate said fluid distributing means to change the cam angle of the tiltable cam plate in response to change in the force moment of the pistons coactable with the cam plate.

4. A fluid pressure energy translating device comprising a housing having inlet and outlet ports, a cylinder barrel rotatably mounted in said housing, pistons reciprocally disposed in said cylinder barrel, a cam plate mounted for tiltable movement in respect to the housing about an axis, biasing means normally urging saidcam plate to tilt.

in one direction, valving means to sequentially connect said pistons with the inlet and outlet ports, said valvingv means including stationary support means, and fluid distributing means interposed between said stationary sup port means and said cylinder barrel, said distributing means including fluid conducting passages defining high and low pressure zones communicating with said inlet and outlet ports, a plurality of said pistons being connected to the high pressure zone with eachexerting a force on said cam plate, the resultant force of said pistons 5. The device of claim 4 further characterized by the resultant force of the pistons which are'communicating with the high pressure zone being movable in, respect to axis of tilt of the cam plate with rotation of the fluid distributing means from said axis to at least one side thereof..

6. The device of claim 5 further characterized by the biasingrneans being located on the other side of the axis' of tilt from the side to which said resultant force is moved. 7. A fluid pressure energy translating devicecomprising a housing having inlet and outlet ports, a cylinder barrel,

rotatably mounted in said housing, pistons reciprocally disposed in said cylinder barrel, a cam plate mounted for tiltable movement in respect to the housing about an axis, biasing means normally urging said cam plate to tilt in one direction, valving means to sequentially connect said pistons with the inlet and outlet ports, said valving means including stationary support means, and fluid distributing means interposed between said stationary support means and said cylinder barrel, mounting means for said fluid distributing means to permit movement of said fluid distributing means in respect to said tiltable cam plate to change the force moment of the pistons on the cam plate in respect to the axis of tilt of the cam plate, fluid actuated control means to impart movement to said fluid distributing means to change the cam angle of the tiltable cam plate in response to change in the force moment of the pistons coactable with the cam plate.

8. A fluid pressure energy translating device comprising a housing having inlet and outlet ports, a cylinder barrel rotatably mounted in said housing, pistons reciprocally disposed in said cylinder barrel, a cam plate mounted for tiltable movement in respect to the housing about an axis, biasing means normally urging said cam plate to tilt in one direction, valving means to sequentially connect said pistons withrthe inlet and outlet ports, said valving means including stationary support means, and fluid distributing means interposed between said stationary support means and said cylinder barrel, mounting means for said fluid distributing means to permit movement of said fluid distributing means in respect to said tiltable cam plate to change the force moment of the pistons on the cam plate in respect to the axis of tilt of the cam plate, pressure responsive control means adapted to move said distributing means responsive to change in the fluid pressure in device to vary the cam angle of the cam plate to maintain a substantially contant fluid pressure at the outlet port.

9. A fluid pressure energy translating device comprising a housing having inlet and outlet ports, a cylinder barrel rotatably mounted in said housing, pistons reciprocally disposed in said cylinder barrel, a cam plate mounted for tiltable movement in respect to the housing about an axis, biasing means normally urging said cam plate to tilt in one direction; valving means to sequentially connect said pistons with the inlet and outlet ports, said valving means including stationary support means, and fluid distributing means interposed between said stationary support means and said cylinder barrel, said distributing means including 1 fluid conducting passages defining high and'low'pressure zones communicating withsaid inlet and outlet ports, a plurality of said pistons being connected to the high pres-S sure zone with each exerting aiforce on said cam plate, the resultant force of said pistonsacting on the cam plate being located by the position oftlie high pressure zone, means journalling said fluid distributing means for rotation in respect to said cam plate'to change the position of said high pressure zone with respect to the axis of tilt 'of the cam plate, and actuation means to rotate said fluid distributing means, said actuating means including a fluid actuated motor operably connected to said distributing means to rotate said distributing means in one direction, and second biasing means operably connected to said distributing means opposing the action of said'fluid motor.

10. The combination of clainr9 further characterized by. said fluid motor including a fluid operated piston and c said second biasing means including a spring;

plate to tilt in one direction, valving means to sequentially connect, said'pistons with the inlet and outlet-ports, said valvingtrneans, including-"stationary support -means, and fluid distributing means. interposed between-said stationary support means and said cylinder barrel, said fluid distributing means including first and 8 second respectively high and low pressure zones communicating with the outlet and inletports, means ontthe support means journalling said fluid distributing means for rotation with respect to said cam plate, said fluid distributing means abutting said support means and said cylinder barrel, con-. trol means to impart rotation to said fluid distributing.

means, vsaid control means includinga fluid operated piston operably connected to said distributing means to "rotate the distributing means in one direction and spring means operably connected to said distributing means op posing said fluid operated piston.

l 12. The device of claim 11 characterized by fluid con-1 ducting means connecting said fluid operated piston tothe high pressure zone of the device to'operate said fluid operated piston responsive to thepressure of the device,

wherebyihefluid distributing means are rotated to vary the cam angle of the cam plate. to maintain substantially t constant fluid pressure atthe outlet port.

References itedby the Examiner UNITED STATES YPATENTS.

2,546,583 3/51 Born 103-162 2,708,879 5/55 Van Meter: 103-162 X 2,749,844 6/56 Wisenbach et'al 103t 162 2,853,025 9/58 Van Meter 103 -162: 2,915,985 12/59 Budz ich' 103 -162 r 3,059,432 10/62 Thoma ,103-162X LAURENCE v. EFNER,'Primary Examiner."

arcuate slots defining, 

1. A FLUID PRESSURE ENERGY TRANSLATING DEVICE COMPRISING A HOUSING HAVING INLET AND OUTLET PORTS, A CYLINDER BARREL ROTATABLY MOUNTED IN SAID HOUSING, PISTONS RECIPROCALLY DISPOSED IN SAID CYLINDER BARREL, A CAM PLATE MOUNTED FOR TILTABLE MOVEMENT IN RESPECT TO THE HOUSING ABOUT AN AXIS, BIASING MEANS NORMALLY URGING SAID CAM PLATE TO TILT IN ONE DIRECTION, VALVING MEANS TO SEQUENTIALLY CONNECT SAID PISTONS WITH THE INLET AND OUTLET PORTS, SAID VALVING MEANS INCLUDING STATIONARY SUPPORT MEANS, AND FLUID DISTRIBUTING MEANS INTERPOSED BETWEEN SAID STATIONARY SUPPORT MEANS AND SAID CYLINDER BARREL, MOUNTING MEANS FOR SAID FLUID DISTRIBUTING MEANS TO PERMIT MOVEMENT OF SAID FLUID DISTRIBUTING MEANS IN RESPECT TO SAID TILTABLE CAM PLATE TO CHANGE THE FORCE MOMENT OF THE PISTONS ON THE CAM PLATE N RESPECT TO THE AXIS OF TILT OF THE CAM PLATE, AND ACTUATION MEANS TO IMPART MOVEMENT TO SAID FLUID DISTRIBUTING MEANS TO CHANGE THE CAM ANGLE OF THE TILTABLE CAM PLATE IN RESPONSE TO CHANGE IN THE FORCE MOMENT OF THE PISTONS COACTABLE WITH THE CAM PLATE. 